Hydraulic system gear pump quick repair method

CB gear pumps are commonly used in agricultural machinery hydraulic systems. After the gear pump is used for a period of time, its performance will drop. Investigation shows that the main form of gear pump damage is the uniform wear and scratches of the shaft sleeve, pump housing and gear, and the average wear amount is generally between 0.02-0.50 mm. Trace depth is generally between 0.05-0.50mm. Due to the limitation of agriculture, there is an urgent need to repair in a short time after damage, and the secondary service life of the gear pump after maintenance, as well as the maintenance cost and on-site operability of maintenance work must also be considered. This article describes arc spray and stick coating techniques for rapid repair methods. Arc Spray Repair Technology for Gear Pumps 1. Principles and Characteristics of Arc Spraying Arc coating technology has developed rapidly in materials, equipment, and applications in the past 20 years. Its working principle is to use two sprayed metal wires as melting electrodes. The variable speed drive causes a short circuit at the gun nozzle to intersect and produce an arc that melts, atomizes into particles with compressed air, and jets at high speed onto the pre-treated work surface to form a coating. It is a kind of spraying method with high spraying efficiency, high bonding strength and good coating quality. It has the advantages of high energy efficiency, low equipment investment and use cost, simple equipment, convenient and flexible operation, convenient on-site construction and safety. 2. Arc Spraying and Repairing Process of Gear Pumps The uniform wear and scratches of the shaft bore, the sleeve outer ring, the gear shaft and the pump housing between 0.02-0.20mm should be used with high hardness and strong combination with parts. , good wear resistance arc spraying repair process. The arc spraying process: pretreatment of the working surface, preheating, spraying the bonding bottom layer, spraying the working layer, cooling, coating processing. In the spraying process, the workpiece is required to be free of oil, rust, rough surface and uniform preheating temperature, the underlying layer is uniformly and firmly bonded, the working layer is smooth and smooth, the material particles are fused and bonded reliably, and the wear resistance and corrosion resistance are good. The quality of the sprayed coating has a lot to do with the surface treatment method and the spraying process. Therefore, it is very important to choose the proper surface treatment and spraying process. In addition, during the spraying and spraying process, the non-sprayed portion adjacent to the surface to be coated is tied with a thin sheet of iron or copper. (1) Pretreatment of the workpiece surface The strength of the bond between the coating and the base is related to the cleanliness and roughness of the substrate. Before spraying, the pretreatment of cleaning, degreasing and surface roughening of the basic surface is an important process in the spraying process. First, the sprayed part should be deoiled with gasoline and acetone, and the fatigue layer and oxide layer should be removed with a trowel, fine sandpaper, and whetstone to expose the metallic color. Then the roughening treatment is performed, and the roughening treatment can provide the surface compressive stress, increase the bonding area of ​​the coating and the substrate and purify the surface, reduce the stress when the coating cools, and relieve the internal stress of the coating, so it is beneficial to the increase of the adhesion force. . Sandblasting is the most commonly used roughening process. The sand is sharp and hard, and quartz sand, corundum, etc. can be used. The rough fresh surface is easily oxidized or contaminated by the environment. Therefore, it must be sprayed in a timely manner. If the surface is over 4 hours, it must be roughened again. (2) Preheating of the surface The temperature difference between the coating and the substrate surface will cause the coating to undergo shrinkage stress, causing the coating to crack and peel off. The preheating of the substrate surface can reduce and prevent the above-mentioned adverse effects. However, the preheating temperature should not be too high, so as to avoid oxidation of the substrate surface and affect the bonding strength of the coating and the substrate surface. Preheating temperature is generally 80-90 °C, commonly used neutral flame. (3) Spray-bonding the base layer A thin layer of metal is sprayed before spraying the working coating to provide a clean, rough surface for the subsequent coating, thereby improving the bond strength and shear strength between the coating and the base body. The adhesion of the underlying material is generally selected chromium iron nickel alloy. The main principle in selecting the coating process parameters is to increase the bond strength between the coating and the substrate. The relative movement speed of the spray gun and the workpiece during the spraying process is greater than the flame moving speed. The speed is determined by the coating thickness, the feeding speed of the sprayed silk body, and the arc power. The distance between the gun and the surface of the workpiece is generally about 150mm. Other parameters for arc spraying are determined by the characteristics of the spray equipment and spray material. (4) The spray coating should be cleaned with a wire brush to remove the deposits on the surface of the bonded substrate, and then spray the working coating immediately. The material is carbon steel and low-alloy wire, so that the coating has a higher wear resistance, and the price is lower. The thickness of the sprayed layer should be determined according to the amount of wear of the workpiece, the machining allowance, and other relevant factors (diameter shrinkage, clamping deviation, unevenness of the sprayed layer diameter, etc.). (5) After the cooling spraying, the temperature rise of the workpiece is not high, and generally it can be directly air cooled. (6) Spray layer processing machine processing to the drawing required size and the specified surface roughness. Surface repair technology of gear pump 1. Adhesion coating principle and characteristics In recent years, surface adhesive coating technology has been widely used in equipment maintenance in China, and is applicable to the repair of parts and equipment of various materials. Its working principle is to directly apply adhesive with special fillers such as molybdenum disulfide, metal powder, ceramic powder and fiber to the surface of materials or parts to make them wearable, corrosion resistant and other functions. It is mainly used for surface hardening and repair. . Its process is simple, convenient and flexible, safe and reliable, does not require special equipment, just coated with a good glue on the cleaned parts surface, after curing, can be trimmed, often at room temperature operation, will not make parts Generates thermal work equivalent effects and deformations. 2. The coating process of the viscous coating has a uniform wear of a small area of ​​0.15-0.50 mm, and a scratch depth of 0.2 mm or more in the outer circumference of the shaft sleeve, the fitting surface of the sleeve end surface, the end surface of the gear end surface, or the inner diameter of the pump housing. At this time, it is advisable to use a tack-coating repair process. The coating process of the adhesive coating: initial cleaning → pre-processing → final cleaning and activation treatment → preparation of repair agent → coating → curing → trimming, cleaning or post-processing. Although the adhesive coating process is relatively simple, the actual construction requirements are quite strict. Only with the selected adhesive, high adhesive strength may not be obtained. It is necessary to choose the right adhesive, but also stick to the right adhesive according to the correct process method, and strictly adhere to the correct process method to achieve satisfactory adhesion. (1) The surface of the initial cleaning parts must not have grease, water, rust, dust, etc. Should be first washed with gasoline, diesel or kerosene, and finally with acetone. (2) The pre-processing uses a fine sand paper to grind a certain groove network to reveal the basic color of the substrate. (3) The final cleaning and activation process is performed with acetone or a special cleaning agent. Then use sandblasting, flame or chemical treatment to increase surface activity. (4) Preparation of Healing Agent The healing agent must be thoroughly mixed with the agent (A) and the curing agent (B) in accordance with the prescribed ratio when used. The color is the same and is used within the prescribed time. (5) The repairing agent for coating is first applied with a thin layer on the surface of the adhesive repair, and is repeatedly scraped so as to fully infiltrate with the components, and then uniformly applied to the prescribed size, leaving a finishing allowance. The coating is moved in one direction as much as possible, and the reciprocal coating encloses the air in the glue to form bubbles or pores. (6) The curing agent is coated with a mold release agent to work on a steel plate. Generally, curing at room temperature requires 24 hours, and heating and curing (about 80° C.) takes 2-3 hours. (7) Finishing, cleaning, or post-processing. Finishing or finishing the bonded surface to the required size with burrs, fine sandpaper, and whetstone.